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JSON to Kotlin Data Class Converter - Online Free | DevToolBox

Free JSON to Kotlin converter. Generate Kotlin data classes from JSON instantly with null safety, @SerialName annotations, and proper type inference. Works with kotlinx.serialization, Moshi, and Gson.

About JSON to Kotlin Conversion

Kotlin data classes provide a concise way to define typed data models. When working with JSON APIs in Kotlin (especially on Android), you need data classes that match the JSON structure. This tool analyzes your JSON and generates idiomatic Kotlin data classes with proper type inference. It handles nullable types for null values, uses List<Type> for arrays, and creates separate data classes for nested objects. The generated code works seamlessly with Kotlinx.serialization, Moshi, or Gson. All processing happens locally in your browser.

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How to Use

  1. Paste your JSON data into the input panel
  2. Set the root class name (default: Root)
  3. Toggle nullable option if needed
  4. Copy the generated Kotlin data classes into your project

Common Use Cases

  • Creating Kotlin data classes for Android API integration
  • Generating models for Ktor server applications
  • Building typed models for Kotlin Multiplatform projects
  • Converting API response samples to Kotlin types

Frequently Asked Questions

How do I convert JSON to Kotlin data classes?
Paste your JSON, set the root class name, and click Convert. The tool generates Kotlin data classes with proper types for each field.
How are nullable types handled?
Fields with null values are typed as nullable (String?). You can also enable the nullable option to make all fields nullable.
Does it work with Android development?
Yes. The generated data classes are compatible with Retrofit, Moshi, Gson, and Kotlinx.serialization commonly used in Android apps.
How are nested objects converted?
Nested JSON objects become separate Kotlin data classes. For example, an address field generates both a Root data class and an Address data class.